High-frequency electrical device



June 12, 1951 J. R. BIRD 2,556,642

HIGH-FREQUENCY ELECTRICAL DEVICE Filed Oct. 2, 1947 FIG. 4

FIG.5

INVENTOR.

JAMES RAYMOND BIRD BY r74 ATTORNE S Patented June 12, 1951 UNITED STATES PATENT OFFICE HIGH-FREQUENCY ELEc'rRIoAL DEVICE James R. Bird, Chagrin Falls, Ohio, assignor to Bird Electronic Corporation, Cleveland, Ohio, a corporation of Ohio Application October 2, 1947, Serial No. 777,516

29 Claims.

7 l s This invention relates to high frequency electri'cal devices and more particularly to high frequency resistors of the coaxial type and to the loading of coaxiallines.

In my c'o pending application for patent, Serial No; 692,116filed August 21, l94 6, now Patent No. 2,552,707, issued May 15, 1951', entitled High Frequency Coaxial Device, there is disclosedan improved coaxial structure fOr use as a resistor in high frequency electrical circuits. In the devi ce of thatca'se the resistance is associated primarily with the inner conductor of the coaxial line, such conductor being in the form of a thin resistive coating on a cylindrical ceramic core. The-outer or return conductor is in the form of atapered tubular horn or shell of thin metal, preferably logarithmic in shape so that the device exhibits pure ohmic characteristics, i. e, an arrangement'in which the surge or characteristic impedance of the line at any point is equal to the resistance of the line measuredbetween the conductors at such point. The inner and outer conductors of the device are tlius so proportioned that at any point along the length of theunit the inductance and capacitance have a relationship such that the characteristic impedance is resistive in nature for all frequencies.

Between the inner resistive conductor and the tapered tubular outer conductor an air dielectrichas heretofore been employed. It has been found, however, that resistive devices so constriieted have limited applications because of the" relatively lowpower absorption exhibited. It is therefore one of the principal objects of the presentinvention to provide an improved method of loadingv coaxial lines employing a high frequency resistive device having relatively large power absorbing and dissipating characteristics. More; specifically, the present invention seeks to provide a resistive device of the character mentioned which exhibits a high rate of power dissipation and absorption while yet being of relativelysimple construction and design and relatively small and compact as well as durable, rugged and economical.

The aboveand other objectives havebeen realized to a large extent in a resistive device having a: coaxial line element which comprises an inner resistive conductor and an outer conductor arranged. in spaced, concentric relation thereto, and in which the space between the conductors contains a liquid dielectric in continuous contact or heat exchangingrelation with the resistive inner. conductor. The method of the" present invention thus involves placing the inner"resistivev conductor of the coaxiarline ele- 2 ment in heat exchanging relation to a body of liquid dielectric having the properties of a coolant. Preferably the inner conductor is immersed in the coolant to heat the latter directly. Liquid dielectric coolant is flowed through the space between the inner and outer conductors of the line element to carry heat away from the relatively hot resistive inner conductor; for example, the heating of the dielectric adjacent the surface of the inner resistive conductor sets up eddy or convective currents in the liquid which carry the heat away from the relatively hot conductor. The outer metal conductor of the coaxial line element absorbs heat from the heated dielectric and dissipates the same to the atmosphere or the outer conductor may also be imme'rsedin the body of liquid dielectric coolant so that convective currents in the liquid outside the outer conductor serve to carry ofi and dissipate the heat. Desirably, and as a further refinem'ent of the invention, the outer conductor is perforated or slotted to provide for convective flow of the liquid dielectric therethrough. The outer conductor may, alternatively, be exposed directly to the cooling effect of ambient air or may be otherwise refrigerated. The bath of liqui'd dielectric is cooled by a circulated refrigeram or by radiant or convective loss of heat to the atmosphere. The embodiment of the invention illustrated in the accompanying drawings, forming a part of this specification, represents a suitable construction for eifec'tuating the above objectives and certain other objectiveshaving to do with details of construction and arrangements of parts which will become apparent as the description proceeds, this description being made by the use of reference numerals which indicate'lik'e parts throughout the several views.

In the drawings:

Figure l is an elevational view, partly in section and with parts broken away and removed, showing a liquid dielectric cooled high frequency electrical resistance device for attachment to a coaxial line;

Fig. 2 is a transverse sectional view with parts removed, taken substantially on the" line indicated at 22 of Fie. 1;

Fig. 3 is a fragmentary sectional detail on an enlarged scale, showing the internal construction of the meansfor' connecting the resistive'device to a coaxial line;

Fig. 4 is a sectional detail showing, on an enlarged scale, the connection of the outer conductor of the coaxial line element to the housing which contains the liquid dielectric; and

Figl'5 is'a sectional'detaiLon an enlarged scale,

showing the connection of the inner resistive conductor to the inner or lead-in connector of the device.

The coaxial line element of the device comprises a hollow cylindrical insulating core I on which is deposited a thin resistive layer or coating 2. The cylindrical core I is of substantially uniform section throughout its length and may be formed of a non-conducting dielectric material such as a glass or ceramic composition like that used in electrical insulators and known as electrical porcelain. The resistive coating 2 forms the inner conductor of the coaxial line and may be in the form of carbon, tungsten, platinum, or other metal applied as by vaporization in rarefied atmosphere, painting of a colloid-dispersion, electrolytic deposition, and by other methods known in sistive coating 2.

the art such as sputtering and sintering. The

coating 2 is sufficiently thin to make electric current flowing through the resistor substantially Y uniform throughout with substantially negligible skin effect.

. Electrical connection to the resistive coating 2 i is made through conductive bands 3 of plated-on metal or of silver or other metal paint. A thin -protective coating of lacquer (not shown) may be applied over the resistive coating 2 and onto adjacent portions but not all of the metal con- .tact bands 3. In th drawings the thickness of the resistive coating 2 and the contact bands 3 has been exaggerated for clarity, it being understood that in actual practice the thickness of these coatings may be little more than molecular in character to avoid objectionable skin effects.

- ance with the disclosure of my prior application referred to above. A suitable material for the outer conductor 4 is copper or brass, preferably the latter, which is formed to the desired shape by spinning or stamping. Small diameter or throat end 5 of the outer conductor or horn embraces the contact band 3 at one end of the inner conductor and the parts are held in assembled relation by a clamp 6 which embraces the horn end.

The large diameter end of the conductor 4 is formed with an integral tubular extension 1 which is of substantially uniform diameter. A housing structure or casing receives the assembled inner and outer conductors of the coaxial line element and forms a reservoir or tank which holds a quantity of liquid dielectric such as mineral oil in which is immersed the inner and outer conductors of the coaxial line element. The housing may be made of material such as sheet steel, copper, or the like and includes a tubular body portion 8 of uniform rectangular section. Flanged caps or end pieces 9 and H] are received telescopically on the central portion 8 of the casing and are welded or soldered in place to provide fluid-tight joints. The casing is of greater height than width and the coaxial line element is disposed in the lower part thereof, the tubular extension 1 of the outer conductor extending through a circular opening II in the end cap 9 of the casing.

A conical or tapered connector I4, also of thin sheet metal, has an offset circular sleeve portion I5 formed integrally on its large diameter end to receive the end of the tubular cylindrical ex- 4 tension 1 of the horn 4. A radial, outwardly directed flange I6 is formed on the sleeve I5 and is clamped against a circular deformable rubberlike sealing gasket 11 by a ring [8 attached to the end cap 9 by circumferentially spaced screws l9 threaded into blind sockets formed in boss elements 2!! carried on the inside of the end cap.

The end of the ceramic core I which is disposed radially inward of the tubular connector 1 of the outer conductor is formed, as by turning in a lathe or by grinding, with a reduced diameter portion 2!. At this end of the core the conductive band 3 of sputtered or plated on metal or of conductive metal paint extend over the reduced diameter end portion 2| of the ceramic core and makes electrical connection with the re- The large diameter end of a tapered inner connector 23 is formed with a hollow shell-like tubular portion 24 telescopically received over the reduced diameter end 2| of the ceramic core. The tubular end of the inner connector embraces the reduced diameter end 2| of the core and is secured thereto by cement 22 which is applied in liquid condition to the inside of the sleeve 24 prior to assembly of the latter onto the core end 2|, the latter being pressed into the sleeve while the cement is soft and held until the cement sets. A band 25 of solder or conductive metal paint is placed about the end of the tubular portion 24 of the connector and is continuous therefrom onto the conductive band 3 to effect a positive electrical connection and a relatively smooth unbroken surface between the parts which comprise the inner conductor of the coaxial line element. The smooth surface connection provided by the band 25 between connector 23 and the conductive band 3 carried by the ceramic core avoids abrupt or sharp diameter changes in the structure of the inner conductor thereby avoiding reflections or other objectionable interference with the electrical characteristics of the line.

At the small diameter end of the outer connector I4 is an integral sleeve-like extension 26 which is received over and soldered to a tubular line coupling member 21, the latter having a conical surface 28 extending into one end thereof as a continuation of the inner conical surface of the outer connector l4. The other end of the coupling member 21 has a reduced diameter portion 29 threaded at 30 to receive an internally threaded attaching collar or ferrule of a coaxial line, not shown.

The tapered inner connector 23 is concentrically or coaxially disposed with respect to the outer connector l4 and has a small diameter cylindrical end portion 32 which extends inside the'outer coupling member 27, and into a central opening in a sleeve or plug 33 of solid dielectric material such as polyethylene or other compound having dielectric properties customarily employed in making solid dielectric coaxial cables.

This plug or spacing element acts as a seal to retain the liquid dielectric within the casing or housing and is formed of material resistant or on the inside of the member 21 at the inner end of the cylindrical bore 34 serves to locate the dielectric plug 33 within the bore. A retaining sleeve 36 having screwdriver slots, one of which is indicated at 4|, is threaded as indicated at 31 into an; enlarged bore 38 within the outer end 29 of the-coupling member, the bore 38 being conone end of the dielectric plug 33 to retain the latter in place in the bore 34 against the pressure of the liquid dielectric which extends into the conical end 28 of the coupling member 21. The

inner end of the sleeve 36 is slightly larger in diameter than the portion 34 of the bore in the connector member and such end of the sleeve is formed with a slot 49 which allows the sleeve to contract as it is forced into place, making a positive electrical connection between the sleeve end. and the internal surface of the bore 34.

The end portion 32 of the inner connector 23 terminates in a reduced diameter extension 39 which telescopically receives one end of a spring metal coupling 40, the parts being soldered together to provide a positive electrical connection. The other end of the coupling 40 is of tubular form diametrically slotted and pinched together so as to resiliently embrace the inner conductor (not shown) of a coaxial line assembled with the device, such coaxial line being held in place by the coupling collar which is threaded on the reduced diameter portion 29 of the outer coupling member 21.

A number of longitudinally extending relatively narrow slots 42 and 43 are formed in the horn or shell 4 which comprises the outer or return conductor of the resistive coaxial line element. The slots are disposed to lie in or be parallel to planes passing through the longitudinal axis of the device so that interference with the high frequency electrical characteristics of the horn 4 is minimized. The slots 43 are located toward the small diameter end of the horn and are fewer in number than the slots 42 located toward the large diameter end of the horn. Although the slots may be equally spaced about the horn circumference, it is preferable that they be concentrated at the top and bottom portions so as to provide a relatively open vertical passage or passages for convective flow through the device to facilitate the flow of the liquid dielectric coolant over the resistive-coating 2 on the ceramic core I.

The resistive coaxial line element of the present 'invention is characterized by the absence of abrupt diameter or dielectric changes throughout its length. That is to say, from the coupling members 21 and 40 to the throat of the horn 4 all diameter changes are gradual or tapered and the dielectric between the inner and outer conductors of the line has substantially the same constant. In accordance with the principles of my prior patent application referred to above and which principles are incorporated herein by reference, the inner and outer connectors 23 and 'l4, constituting the transition zone of the coaxial line element, are each uniformly tapered between the coupling members 40 and 21 and the points of connection to the cylindrical zones of the conductors at the open or entrance end of the resistive portion or zone of the line. The cylindrical portion of the inner conductor comprises the tube 24 and conductive bands 3, and 25, while the cylindrical portion of the outer conductor comprises the tubular extension 1 on the end of the horn.

Various liquids such as transformer oil and silicones may be used for the dielectric coolant in the present resistive device. It is preferable, however, to use liquids having relatively low dielectric constants, constantsof-the order of about I in the space between the inner and outer conductors of the line element which has substantially the same dielectric constant as the solid plug 33 avoids the objectionable effects of an abrupt change in dielectric at the entrance end of the transition zone. For example, the plug 33 may be made ofpolytetrafluoroethylene or a compound known commercially as Teflon having a dielectric constant: e:2.05. The liquid dielectriccoolant used to immerse the conductors of theresis-tive coaxial line is a mineral oil such as that soldcornmercially for medicinal purposes and known as Nujol having a dielectric constant: e=2.'15. Such a mineral oil functions efliciently not only as a dielectric, the constant of which is taken into consideration in calculating the dimensions and curvature of the outer conductor or horn 4 in accordance with the principles heretofore mentioned, but also serves as a coolant -forconvectively removing absorbed heat from the resistive inner conductor or coating 2- on the ceramic core I of the coaxial line element. The mineral oil dielectric functions effectively as a coolant by reason of its high specific heat or heat absorbing characteristics and its low viscosity which promotes the flow of convective currents that remove heat rapidly from adjacent the inner conductor.

When the device of the present invention is utilized as a line terminator in a coaxial electrical circuit, connections being made to a coaxial cable or line through the coupling members 21 and 40, high frequency current flowing into the device has the effect of heating the resistive coating 2. The liquid dielectric which completely engulfs the inner conductor and the outer conductor or horn 4 of the coaxial line element is heated adjacent the resistive coating 2 by physical contact therewith or with the thin protective lacquer coat. The heated portions of the liquid dielectric then rise upwardly through the space between the inner and outer conductors of the line element and through the slots 42 and 43 in the upper portions of the horn 4. Fresh or relatively cool dielectric flows upwardly through the slots 42 and 43 in the bottom portion of the horn into the space between the conductors of the line element to replace the heated liquid. This convective flow of liquid dielectric over the relatively hot resistive coating 2 promotes a continuous flow or circulation of the liquid dielectric into and out ofthe horn 4 and throughout the entire body of the liquid dielectric within the housing. The flow of the dielectric over the heat conducting metal of the outer metal or horn 4 has the effect of heating the latter, all portions of the horn tending to remain at substantially the same temperature because of the high heat conductivity thereof. Liquid dielectric that is in contact with the metal of the horn and is at a lower temperature is heated thereby to rise and set up further convective flow within the body of liquid dielectric contained in the housing.

The flow of the relatively hot liquid dielectric over the inside surfaces of the walls of the casing body 8 and end caps 9 and I0 heats the latter. In this manner the liquid dielectric is cooled and flows downwardly to the bottom of the casing and thence upwardly through the horn openings 42 and 43 to again be heated by the relatively hot or, perforated spacer.

resistive coating 2 of the inner conductor and the cycle is repeated. The walls of the body 8 and the end caps 9 and IU of the casing lose heat to the atmosphere by radiation and by the flow of ambient air thereover. A dull black paint applied over the outside of the casing promotes the loss of heat therefrom and increases the heat or power dissipating capacity of the device.

Another method of withdrawing heat from the liquid dielectric, especially useful in applications requiring high load capacity, employs circulating lquid or fluid refrigerant in heat exchanging relation thereto. For this purpose a fluid or refrigerant conductor 44 is immersed in the liquid dielectric above the coaxial line element, the upper surface of the liquid dielectric being indicated at45. Metal fins 46 which may be in the form of a continuous helical coil brazed or soldered on the outside of the conduit 44 promote the exchange of heat between the liquid dielectric in the housing and a liquid refrigerant or coolant such as water which is circulated through the conduit 44 from a suitable source, not shown. The conductor 44 may be of U shape in plan form having both inlet and outlet ends extending through the end cap Ill and attached to the latter by compression sleeve members 41. An air space 48 above the surface of the liquid provides for expansion and contraction of the latter within the metal casing as the temperature of the liquid dielectric varies. A filler plug 50 in the top of the casing may incorporate an excess pressure safety release to avoid damage, and a carrying handle 51 is attached to cleats 52 on the top of the casing. In the present resistive device the liquid dielectrio which also serves as a heat transfer medium is continuous not only over the entire length of the inner resistive conductor of the coaxial element, but also into the hollow tapered connector 4 [4 so that an extremely accurate and efficient line element results without abrupt diameter or dielectric changes. If desired, the resistor may be connected to a coaxial line or cable employing a liquid dielectric, the solid plug or sealing member 33 being omitted or replaced by a spider-like Although the elongated slots or perforations 42 and 43 in the logarithmic horn 4i (or such equivalent openings or passages as may be provided) effect rapid withdrawal of heated dielectric from the space between the inner and outer conductors of the coaxial line element, he device functions Well without the slots, although with less heat and power dissipating capacity. Without the perforations the heat conducting properties of the metal shell 4 are relied upon to transferthe heat from liquid dielectric within the shell 4 to liquid coolant outside the same, the operation and construction otherwise being the same.

The principles of the present invention may be utilized in various ways, numerous modifications and alterations being contemplated, substitution of parts and changes in construction being resorted to as desired, it being understood that the embodiment shown in the drawings and described above and the particular method set forth are tions comprising an insulating core having a coating thereon of relatively high electrical resistance,

; a tapered sleeve of electrical and heat conducting material surrounding the coated core and connected thereto at one end, a body of dielectric convective liquid in the space between the resistive coating and the sleeve for convectively removing heat from said coating and carrying such heat to the sleeve, casing means enclosing the liquid dielectric body and substantially surrounding the core and the sleeve, the dielectric substantially filling the space between the tapered sleeve and the core, and means for cooling the sleeve.

2. A resistive device for high frequency applications comprising a tapered conductive shell of generally circular cross section and having elongated slots therein, a cylindrical resistor disposed within the shell and at one end making electrical connection with the small diameter end of the shell, means at the other ends of the shell and the resistor for connecting the same to a coaxial line, housing means for enclosing the shell and the resistor, and a liquid dielectric in the housing means and submerging the shell and the resistor, whereby the liquid dielectric is maintained in heat exchanging relation to the resistor and is fiowable through the shell slots in carrying heat away from the resistor.

3. A resistive device for high frequency application comprising a casing having an opening in one end thereof, a coaxial line element disposed in said casing and having a perforated outer conductor, the line element extending through said opening and making a fluid tight seal therewith, one end only of the outer conductor being rigidly secured to the casing at the opening to support the line element cantilever fashion in predetermined. position within the casing, and a liquid dielectric in the casing for cooling the line element, the liquid being continuous through the perforations of the outer conductor.

4. A resistive device for high frequency application comprising a casing having an opening in one end thereof, a coaxial line element disposed in said casing and having a perforated outer conductor, the line element extending through said opening and making a fluid tight seal therewith, one end only of the outer conductor being rigidly secured to the casing at the opening to support theline element cantilever fashion in predetermined position within the casing, a liquid dielectric in the casing for cooling the line element, the liquid being continuous through the perforations of the outer conductor, and means for conducting a liquid coolant in heat exchanging relation to the liquid dielectric.

5. A high frequency electrical device comprising a tapered metal shell and a substantially cylindrical resistor assembled in concentric relation, one end of the shell embracing and making electrical contact with one end of the resistor, a housing having a chamber enclosing the assembly, a liquid dielectric in the chamber, the shell having openings therein for the admission of the liquid dielectric to permit the flow of liquid dielectrio over the resistor in conducting heat therefrom, and means making electrical connection to the other ends of the shell and the resistor for incorporating the device in a high frequency circuit.

6. A resistive device for high frequency applications comprising inner and outer conductors arranged in a spaced coaxial relation and connected together at one end, at least one of the conductors being resistive in character and at least one of the conductors being tapered so that the characteristic impedance at any point across the device is substantially equal to the resistance measured between the conductors at such point, inner and tubular outer connectors connected at one end to the other ends of the conductors for connecting the latter to a coaxial line, said connectors being spaced from one another in substantially concentric relation, a liquid dielectric continuous in the spaces between the conductors and the connectors and in direct heat exchanging contact with the resistive conductor to cool the same, a plug of solid dielectric material at the other end of the connectors closing the space between the connectors to seal the liquid dielectric from a connected coaxial line, and means in heat exchanging relation with the liquid dielectric for cooling the same.

7. A resistive device for high frequency applications comprising a tapered conductive horn, a substantially cylindrical resistor arranged in spaced, coaxial relation to the horn and connected thereto at one end, a pair of spaced, coaxial connectors on the other ends of the horn and resistor for connecting them to a coaxial line, one of the connectors being tapered, a liquid dielectric in the space between the horn and the resistor and in heat exchanging relation with the resistor to ,cool the latter, said dielectric being continuous into the space between the connectors, a solid dielectric plug and means mounting the same to seal the space between the connectors, and means inheat exchanging relation with the liquid dielectric for cooling the same.

8. A resistive device for high frequency applications comprising a tapered conductive horn, a

substantially cylindrical resistor arranged in spaced, coaxialrelation to the horn and connected thereto at one end, a pair of spaced, coaxial connectors on the other ends of the horn and resistor for connecting them to a coaxial line, one of the connectors being tapered, a liquid dielectric in the space between thehorn and the resistor and in heat exchanging relation with the resistor to cool the latter, saiddielectric being continuous into the space between the connectors, a solid dielectric plug and means mounting the same to seal the space between the connectors, and means having a dielectric constant substantially the same as that of the liquid dielectric, and means in heat exchanging relation with the liquid dielectric for cooling the same.

9. The method of dissipating heat in a high frequency coaxial line termination having an inner resistive coating conductor that is heated by electrical current and an outer surrounding metal horn conductor concentric to and spaced from the inner conductor, every point along the line termination having a calculated characteristic impedance substantially equal to the resistance of the line termination measured between the conductors at such point, which method comprises circulating in the space between the conductors and in direct, substantially continuous contacting heat exchanging relation to the resistive coating conductor a body of liquid dielectric having electrical properties directly related to the calculating characteristic of the line termination, and circulating a cooling fluid about the outside of the metal horn conductor in direct heat exchanging contact therewith whereby the 'horn absorbs heat from the circulating liquid dielectric and the heated horn is cooled by the circlulating cooling fluid.

10. The method of dissipating heat in a high frequency coaxial line termination having an in- ,ner resistive coating conductor that is heated by electrical current and an outer surrounding metal horn conductor concentric to and spaced from the inner conductor, every point along the line termination having a calculated characteristic impedance substantially equal to the resistance of the line termination measured between the conductors at such point, which method comprises maintaining the conductors immersed in a body of liquid dielectric having electrical properties directly related to the calculated characteristics of the line termination so that such dielectric substantially fills the space between the conductors and is in substantially continuous direct contacting heat exchanging relation to the resistive coating conductor, continuously circulating the liquid dielectric into and out of said space through the horn to displace dielectric heated by the resistive conductor, and continuously cooling the displaced dielectric externally of the horn.

11. The method of dissipating heat in a coaxial line termination having calculated characteristics, the line termination being of the type having an inner resistive coating conductor that is heated by electrical current and an outer surrounding conductor concentric to and spaced from the inner conductor which comprises maintaining in the space between the conductors and in direct, substantially continuous contacting heat exchanging relation to the resistive coating conductor a body of liquid dielectric having electrical properties directly related to the calculated characteristics of the line termination, and continuously circulating liquid dielectric into and out Of said space to continuously remove dielectric heated by said contact with the resistive coating conductor.

12. The method of dissipating heat in a coaxia1 line termination having calculated characteristics, the line termination being of the type having an inner resistive coating conductor that is heated by electrical current and an outer surrounding conductor concentric to and spaced from the inner conductor which comprises maintaining in the space between the conductors and in direct, substantially continuous contacting heat exchanging relation to the resistive coating conductor a body 'of liquid dielectric having electrical properties directly related to the calculated characteristics of the line termination, continuously circulating liquid dielectric into and out of said space to continuously remove dielectric heated by said contact with the resistive coating conductor, and continuously cooling removed dielectric and returning the cooled dielectric to said space.

13. The method of dissipating heat in a coaxial line termination having calculated characteristics, the line termination being of the type having an inner resistive material conductor that is heated by electrical current and an outer surrounding conductor concentric to and spaced from the inner conductor which comprises circulating a confined body of liquid dielectric having electrical properties including a dielectric constant of the order of about 6:5 or less directly related to the calculated characteristics of the line termination in the space between the conductors and in direct, substantially continuous contacting heat exchanging relation to the resistive material conductor to absorb heat therefrom while maintaining said space substantially full of said dielectric liquid, flowing a portion of the liquid dielectric into and out of a space other than the space between the said inner and outer conductors to accommodate expansion and con traction of the liquid dielectric incident to heating and cooling, and continuously cooling the circulating liquid dielectric to remove absorbed heat.

14. The method of dissipating heat in a coaxial line termination having calculated characteristics, the line termination being of the type having inner and outer coaxial conductors, the outer conductor being spaced from and concentric to the inner conductor and one of the conductors comprising a resistive material that is heated by electrical current, which method comprises maintaining in the space between the conductors and in direct, substantially continuous contacting heat exchanging relation to the resistive material a confined body of liquid dielectric having electrical properties including a dielectric constant of the order of about 6:5 or less directly related to the calculated characteristics of the line termination, and continuously circulating such liquid dielectric into and out of said space while maintaining said space substantially full of dielectric liquid to continuous- 'ly remove dielectric heated by said contact with g the resistive material.

15. The method of dissipating heat in a coaxial line termination having calculated characteristics, the line termination being of the type having inner and outer coaxial conductors, the outer conductor being spaced from and concentric to the inner conductor and one of the conductors comprising a, resistive material that is heated by electrical current, which method comprises circulating a confined body of liquid dielectric having electrical properties including a dielectric constant of the order of about e=5 or less directly related to the calculated characteristics of the line termination in the space between the conductors and in direct, substantially continuous contacting heat exchanging relation to .the resistive material to absorb heat therefrom while maintaining said space substantially full of said dielectric liquid, flowing a portion of the liquid dielectric into and out of a space other than the space between the said inner and outer conductors to accommodate expansion and contraction of the liquid dielectric incident to heating and cooling, and continuously cooling the circulating liquid dielectric to remove absorbed heat. 16. In an electrical high frequency resistive de- -vice, a coaxial line comprising inner and outer conductors, the outer conductor being concentric to the inner conductor and separated therefrom by an annular space, one of the conductors comprising a resistive material, one of the conductors being tapered along its length to provide substantially non-reflecting calculated line characteristics, and a liquid dielectric coolant having -'electrical properties directly related to the cal- :culated line characteristics disposed in and substantially filling the space between the conductors and in contacting heat exchanging relation to the resistive material for convectively cooling the resistive material conductor, the device including substantially liquid tight means confining said liquid dielectric coolant in a substantially continuous body substantially excluding the atmosphere from said annular space and means permitting flow of said liquid dielectric into and out of a space other than said annular space to accommodate expansion and contraction of such liquid.

17. In an electrical high frequency resistive deivice, a coaxial line comprising inner and outer conductors, the outer conductor being concentric to the inner conductor and separated therefrom by an annular space, the outer conductor being tapered along its length to provide substantially non-reflecting calculated line characteristics and the inner conductor comprising a resistive material, and a liquid dielectrical coolant having electrical properties directly related to the calculated line characteristics disposed in and substantially filling the space between the conductors and in contacting heat exchanging relation to the resistive material for convectively cooling the inner conductor, the device including substantially liquid tight means confining said liquid dielectric coolant in a substantially continuous body substantially excluding the atmosphere from said annular space and means per mitting flow of said liquid dielectric into and out of a space other than said annular space to accommodate expansion and contraction of such liquid.

I 18. In an electrical high frequency resistive device, a coaxial line comprising inner and outer conductors, the outer conductor being concentrio to the inner conductor and separated therefrom by an annular space, one of the conductors comprising a resistive material, one of the conductors being tapered along its length to provide substantially non-reflecting calculated line characteristics, and a liquid dielectric coolant having a dielectric constant of the order of e=5 or less directly related to the calculated line char acteristics disposed in and substantially filling the space between the conductors and in con tacting heat exchanging relation to the resistive material for convectively cooling the resistive material conductor, the device including substantially liquid tight means confining said liquid dielectric coolant in a. substantially continuous body substantially excluding the atmosphere from said annular space and means permitting flow of said liquid dielectric into and out of a space other than said annular space to accommodate expansion and contraction of such liquid.

19. A high frequency electrical resistive device comprising a tapered outer conductor and a substantially cylindrical inner resistive conductor assembled concentrically in spaced relation as a coaxial line, substantially every point along the line having a calculated characteristic impedance substantially equal to the resistance of the line measured between the conductors at such point, a housing having a chamber sub stantially enclosing the assembly, a liquid dielectric coolant in and limited to the chamber, said liquid having electrical properties directly related to the calculated characteristics of the line, the outer conductor having openings therethrough to admit the dielectric liquid into the space between the conductors to flow over the resistive conductor in convectively cooling such resistive conductor, and means making electrical connection to the ends of the inner and outer conductors for incorporating the device in a high vice measured between the conductors at corresponding .points, means for connecting corresponding ends of the conductors to the coaxial line conductor elements, a liquid dielectric coolant having electrical properties directly related to the calculated characteristics of the device disposed in and substantially filling the space between the conductors and in substantially direct heat exchanging contact with the resistive material conductor to convectively cool the latter, and a solid dielectric sealing plug having a dielectric constant substantially equal to the dielectric constant of the liquid coolant supported by the connecting means to prevent the flow of the liquid dielectric from the space between the conductors into the coaxial line, the device including substantially liquid tight means confining said liquid dielectric coolant in a substantially continuous body substantially excluding the atmosphere from said space between the inner and outer conductors and means permitting flow of said liquid dielectric into and out of a space other than said space between the inner and outer conductors to accommodate expansion and contraction of such liquid.

21. Ahigh frequency electrical resistive device comprising a, tapered outer conductor and a resistive material inner conductor assembled concentrically in spaced relation as a coaxial line, a casing surrounding the conductors and defining an enclosing chamber for confining a fluid dielectric, means securing the outer conductor to the casing for supporting the assembled line in the casing, and a plurality of spaced apertures through the outer tapered conductor for the flow of fluid dielectric confined within the casing chamber through the space separating the conductors for direct heat exchanging contact with the resistive material inner conductor in convectively cooling thelatter.

22. A high frequency electrical resistive device comprising a tapered outer conductor and a resistive material inner conductor assembled concentrically in spaced relation as a coaxial line, a casing surrounding the conductors and defining an enclosing chamber for confining a fluid dielectric, an opening in the casing, means securing one end of the outer conductor over the casing opening as a closure therefore and to support the coaxial line cantilever fashion within the casing, and a plurality of spaced apertures through the outer tapered conductor .for the flow of fluid dielectric confined within the casing chamber through the space separating the conductors for direct heat exchanging contact with the resistive material inner conductor in convectively cooling the latter.

23. An electrical high frequency resistive de vice comprising inner and outer conductors arranged concentrically in spaced coaxial relation, at least one of the conductors being of resistive material and at least one of the conductors being tapered along its length to provide a calculated characteristic impedance substantially at all points across the conductors substantially equal to the resistance of the device measured between the conductors at corresponding points, and a mineral oil liquid coolant having electrical properties including a dielectric constant of the order ofabout e= or less directly related to the calculated characteristics of the device disposed in and substantially filling the space between the conductors and in substantially direct heat exchanging conta-ct with the resistive material conductor to conyectively cool the latter, the device including substantially liquid tight mean confining said liquid dielectric coolant in a substantially continuous body substantially excluding the atmosphere from the space between the coaxial conductors and means permitting flow of said liquid dielectric into and out of another space to accommodate expansion and contraction of such liquid.

24. An electrical high frequency resistive device comprising an elongated inner conductor of resistive material, an outer tubular conductor of metal having relatively high heat conductivity coaxial to the inner conductor and spaced therefrom to form therewith a coaxial line, the outer conductor being tapered along its length to provide in the line a calculated characteristic impedance substantially at all points across the conductors substantially equal to the resistance of the device measured between the conductors at corresponding points, and a mineral oil liquid coolant having electrical properties including a dielectric constant of the order of about e=5 or less directly related to the calculated characteristics of the device disposed in and substantially filling the space between the conductors and in substantially direct heat exchanging contact with the resistive material conductor to convectively cool the latter, the liquid dielectric coolant also being in substantially direct heat exchanging contact with the metal outer conductor along substantially the entire tapered length of the latter for the transfer of heat therebetween and for the rapid equalizing of temperature along the length of the device.

25. For use in combination with a coaxial line of the type having spaced concentric inner and outer conductor elements, an electrical high frequenc resistive device comprising inner and outer conductors arranged concentrically in spaced coaxial relation, at least one of the conductors being of resistive material and at least one of the conductors being tapered along its length to provide a calculated characteristic impedance substantially at all points across the conductors substantially equal to the resistance of the device measured between the conductors at corresponding points, means for connecting corresponding ends of the conductors to the coaxial line conductor elements, a mineral oil liquid coolant having electrical properties including a dielectric constant of the order of about e=5 or less directly related to the calculated characteristics of the device disposed in and substantially filling the space between the conductors and in substantially direct heat exchanging contact with the resistive material conductor to convectively cool the latter, and a solid dielectric sealing plug having a dielectric constant substantially the same as that of the dielectric liquid coolant supported by the connecting means to prevent the flow of such liquid from the space between the conductors into the coaxial line.

26. An electrical high frequency resistive device comprising a casing having an opening in one wall thereof, a coaxial line element disposed in the casing and including inner and outer conductors arranged in spaced coaxial relation, at least one of the conductors being resistive in character at least one of the conductors being tapered so that the characteristic impedance of the line at any point is substantially equal to the resistance measured between the conductor at such point, one end of the outer conductor being positioned across the casing opening on the inside of the casing, inner and tubular outer connectors coaxially arranged and connected respectively to and aligned with the inner and outer conductors for connecting the latter to a coaxial transmission line or the like, said connectors being spaced from one another and the outer connector being positioned across the casing opening on the outside of the casing, a liquid dielectric coolant in the casing and immersing both the inner and the outer conductors, said liquid being continuous in the spaces between the conductors and the connectors and in substantially direct heat exchanging contact with the resistive conductor to cool the latter, and a sealing plug of dielectric material supported in the space between the connectors.

27. An electrical high frequency resistive device comprising a casing having walls defining a substantially liquid tight chamber, an electrical line element disposed in the chamber, said line element including inner and outer conductors arranged in spaced coaxial relation, at least one of the conductors being resistive in character and at least one of the conductors being tapered to provide at points spaced along the length of the line calculated characteristic impedances substantially equal to the resistances of the line measured between the conductors at the respective points, inner and outer connectors arranged one within the other in coaxial spaced relation and connected respectively to and aligned respectively with the inner and outer conductors for connecting the latter to a coaxial transmission line or the like, the connectors being tapered to provide gradual changes in diameter between such transmission line and the conductors of the line element, one of the walls of the casing being formed with an opening, one end of the outer connector and one end of the outer conductor being disposed across the wall opening in confronting relation to one another with the outer connector generally on the outside of the easing and the outer conductor generally on the inside of the casing, liquid coolant means in the casing and immersing both the inner and the outer conductors, said liquid means being substantially continuous in and substantially filling the spaces between the conductors and the connectors and in such spaces having a dielectric constant directly related to the calculated impedance characteristics of the line element, said liquid means also being substantially in direct heat exchanging contact with the resistive conductor to cool the latter, and solid dielectric means between the connectors to support and space the inner connector in axial concentric re- I provide at points spaced along the length of the line calculated characteristic impedances substantially equal to the resistances of the line measured between the conductors at the respective points, inner and outer connectors arranged one within the other in coaxial spaced relation and connected respectively to and aligned respectively with the inner and outer conductors for connecting the latter to a coaxial transmission line or the like, the connectors being tapered to provide gradual changes in diameter between such transmission line and the conductors of the line element, one of the walls of the casing being formed with an opening, one end of the outer connector and one end of the outer conductor being disposed across the wall opening in confronting relation to one another with the outer connector generally on the outside of the casing and the outer conductor generally on the inside of the casing, liquid coolant means in the casing and immersing both the inner and the outer conductors, said liquid means substantially completely filling the space between the coaxial conductors and in such space having a dielectric constant directly related to the calculated impedance characteristics of the line element and being substantially in direct heat exchanging contact with the resistive conductor to cool the later, and solid dielectric means effecting a seal between the connectors to prevent loss of the liquid means from the space between the conductors.

29. An electrical high frequency resistive device comprising a casing having walls defining a substantially liquid tight chamber, an electrical line element disposed in the chamber, said line element including inner and outer conductors arranged in spaced coaxial relation, at least one of the conductors being resistive in character and at least one of the conductors being tapered to provide at points spaced along the length of the line calculated characteristic impedances substantially equal to the resistances of the line measured between the conductors at the respective points, inner and outer connectors arranged one within the other in coaxial spaced relation and connected respectively to and aligned respectively with the inner and outer conductors for connecting the latter to a coaxial transmission line or the like, the connectors being tapered to provide gradual changes in diameter between such transmission line and the conductors of the line element, one of the walls of the casing being formed with an opening, one end of the outer connector and one end of the outer conductor being disposed across the wall opening in confronting relation to one another with the outer connector generally on the outside of the casing and the outer conductor generally on the inside of the casing, said ends of the outer connector and the outer conductor being secured to the apertured casing wall with the outer connector and the outer conductor substantially wholly supported by the wall as cantilevers and with the connected inner connector and inner conductor forming a center assembly extending through the wall opening, said center assembly being supported at opposite ends on opposite sides of the wall, one end by the outer connector on one side of the wall and the other end by the outer conductor on the other side of the wall, and being substantially unsupported between its ends, liquid coolant means in the casing and immersing both the inner and the outer conductors, said liquid means substantially completely filling the space between the coaxial conductors and in such space having a dielectric constant directly related to the calculated impedance characteristics of the line element and being substantially in direct heat exchanging contact with the resistive conductor to cool the latter, and solid dielectric means efiecting a seal between the connectors to prevent loss of the liquid means from the space between the conductors.

JAMES R. BIRD.

(References on following page) 17 REFERENCES CITED Number The following references are of record in the 2400777 file of this patent: UNITED STATES PATENTS Number Name Date 2,441,165 2,029,421 Green et a1 Feb. 4, 1936 2,4 2,147,481 Bettlestone Feb. 14, 1939 2,273,547 Van Radinger Feb. 17, 1942 2,399,645 Latimer May 7, 1946 10 Number 2,399,930 Keister May '2, 1946 191,794

Name Date Okress May 21, 1946 Tiley et a1. Oct. 15, 1946 Ovrebo June 10, 1947 Salisbury Aug. 19, 1947 Ovrebo May 11, 1948 Tiley Nov. 9, 1948 FOREIGN PATENTS Country Date Great Britain Sept. 6, 1938 

